Spinal surgeries are commonly used in the medical profession to treat spinal conditions that result when functional segmental units of the spine are moved out of proper position or otherwise damaged. Examples of procedures used to treat spinal conditions include disc replacement, laminectomy, and spinal fusion.
Following certain spinal procedures, such as spinal fusion, it is typically desirable to stabilize the spine by preventing movement between the vertebrae while the spine heals. This act of stabilizing the spine by holding bones in place during healing has greatly improved the success rate of spinal fusions and other procedures.
With spinal stabilization procedures, a combination of metal screws and rods creates a solid “brace” that holds the vertebrae in place. These devices are intended to stop movement from occurring between the vertebrae. These metal devices give more stability to the fusion site and allow the patient to be out of bed much sooner.
During the spinal stabilization procedure, pedicle screws are placed through the pedicles on the posterior portion of two or more vertebrae of the spinal column. The screws grab into the bone of the vertebral bodies, giving them a good solid hold on the vertebrae. Once the screws are placed on the vertebrae, they are attached to metal rods that connect all the screws together. When everything is bolted together and tightened, the assembly creates a stiff metal frame that holds the vertebrae still so that healing can occur.
Posterior dynamic stabilization (PDS) generally refers to such a stabilization procedure where dynamic rods are positioned between the pedicle screws. These dynamic rods can generally bend, extend, compress, or otherwise deform in order to allow some limited movement between the pedicle screws. By allowing this limited movement between the pedicle screws and the associated vertebrae, less strain is placed on adjoining, non-stabilized functional segmental units during patient movements. In addition, the dynamic rod generally decreases the stresses on the screw shank, minimizing the possibility of screw backout or related screw failures. However, even with dynamic rods, stresses are experienced by the screw shank which could potentially result in screw backout or related failures under the appropriate circumstances. Accordingly, it would be desirable to provide a PDS system capable of further protecting the screw-bone interface and reducing the chances of screw backout. For example, it would be advantageous to provide a PDS system with a flexible stabilization element that offers different kinematics and loading requirements from those stabilization elements found in the prior art. Such a stabilization element would offer additional options to the surgeon when traditional PDS stabilization elements appear problematic.